Immunotherapies and their use in prostate cancer

The authors aimed to review immunotherapies available for prostate cancer treatment.

The authors concluded that further research into immunotherapy for prostate cancer is needed to more accurately assess the effect of immunotherapies as a viable treatment option for prostate cancer.

Targeting the immune system is a treatment option in many types of cancer. Immunotherapy targets certain parts of the immune system, helping it to recognize and attack attacking specific cancer cells. This may be done by blocking proteins, or attaching antibodies to particular proteins on the cancer cell. Cancer vaccines are also under development.

Immunotherapy options have not been as successful in prostate cancer as in other forms of cancer. Further research is needed to identify the optimum immunotherapy for men with prostate cancer.

The aim of this study was to review the immunotherapies available for prostate cancer treatment.

Sipuleucel-T (Provenge) is a vaccine used to treat men with low-risk, no-symptom prostate cancer. This vaccine involves immune cells removed directly from the patient, which are then primed to attack certain proteins on the cancer cells. These cells are then reinfused back into the patient. Treatment with sipuleucel-T was shown to improve overall survival (OS – time from treatment until death from any cause) by 4.1 months, with a 22% reduced risk of death. It was also well tolerated with no severe side-effects.

PROSTVAC-VF (Tricom) is a vaccine that targets prostate specific antigen (PSA – protein elevated in the presence of prostate cancer). It was shown to improve PSA progression-free survival (PFS – time from treatment until disease progression) in 63% of patients for more than 6 months. It also slowed the PSA doubling time from 5.3 months to 7.7 months in patients with localized cancer. In another study, OS was significantly increased by 8.5 months after 3 years of follow-up.

Personalised peptide vaccines (PPV) activate an anti-tumor response that kills cancer cells. In one study, PFS improved from 2.8 months to 8.5 months. The most common side-effect was injection-site reaction.

Ipilimumab (Yervoy) is a monoclonal antibody that allows natural immune cells to target and kill cancer cells. Patients treated with ipilimumab experienced a PFS of 4 months compared to 3.1 months in the placebo group (group that did not receive the active vaccine). Patients also more frequently had a greater than 50% reduction in PSA. Overall OS was not significantly improved. In a subgroup of patients with few risk factors, the average OS was 22.7 months in the ipilimumab group compared to 15.8 months in the placebo group.

Tasquinimod (ABR-215050) blocks a protein used in cancer cell growth. In a study conducted with 206 patients who showed little or no symptoms, and who had not been treated with chemotherapy, tasquinimod significantly delayed disease progression from 3.3 months to 7.6 months.

Current and future trials will be examining combinations of immunotherapies, as well as searching for certain biomarkers (genetic or molecular markers) that may indicate patients who would benefit from immunotherapy. 

The authors concluded that further research into immunotherapy for prostate cancer is needed to more accurately assess the effect of immunotherapies as a viable treatment option for prostate cancer.